1. Field of the Invention
The present invention relates to a reciprocating actuator with a directional control valve that minimizes the length of the actuator by eliminating the need for an auxiliary cylinder in the actuator assembly.
2. Description of the Prior Art
A conventional reciprocating type actuator, such as the one disclosed in Japanese Utility Model Publication No. 37829/1986, has a configuration comprising a single-rod type piston slidably fitted in a cylinder with a directional control valve mechanism attached to the piston. Valve mechanism switching, at each end of reciprocating stroke, transfers a working fluid into the alternate of two working fluid chambers formed in the cylinder and separated from each other by the piston.
A conventional reciprocating actuator must have an auxiliary cylinder below the main cylinder into which the piston is retracted. The auxiliary cylinder has an axial length sufficient for the full stroke length of the piston so that when the piston moves upward, discharge of working fluid above the piston is accomplished regardless of the position of the piston. A reciprocating actuator having a directional control valve mechanism attached to the piston, such as the above example, requires that the actuator assembly have sufficient length in the axial direction, as determined by the length of the discharge auxiliary cylinder, to enable discharge.